* {
    margin: 0;
    padding: 0;
    font-size: 14px;
}

.btn {
    background-color: #ccc;
    width: 36px;
    height: 18px;
    display: inline-block;
    border-radius: 10px;
    cursor: pointer;
}

span {
    width: 18px;
    height: 18px;
    background-color: #fff;
    border-radius: 10px;
    display: block;
}

.open {
    background-color: aquamarine;
    text-align: center;
}

#open_span {
    float: right;
}

li {
    padding: 5px 10px;
    list-style: none;
}